Barack Obama may have ruled out sending "boots on the ground" back to Iraq but in the face of a growing threat from the Islamic State (IS), the Pentagon appears to have hit upon a way to get them back in by the back door.

The US Army's Contracting Command has issued a tender notice for companies capable of deploying security assistance mentors and advisers in Iraq.

These individuals would be required for a 12-month contract, potentially extendable to a total of 36 months.

They are needed as consultants to the US "Office of Security Assistance in Iraq" and must be "cognisant of the goals of ... reducing tensions between Arabs and Kurds, and Sunnis and Shias".

Some 40,000 private security contractors formed a disparate mercenary army of mostly westerners during the American-led occupation of Iraq.

Image:Private security guards may be set to return to Iraq. Pic: Pete Norman

Many had secret contracts to work with the Central Intelligence Agency and alongside US and British special forces to provide intelligence and guard forces.

Now it appears that former special forces operators and other highly skilled intelligence specialists are being recruited to return to Iraq.

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Intelligence sources have told Sky News the only viable option to fight back against the spread of the IS is to restart the so-called Awakening programme which, by late 2008, had successfully mobilised Sunni tribesmen against al Qaeda.

The rump of al Qaeda fled to Syria where it became the core of what is now IS.

The new consultants would be required to conduct "force development", "training", "planning and operations" and "intelligence".

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They would liaise with the Iraqi Ministry of Defence, its Counter Terrorism Service and other branches of government.

The "sources sought" document was published on August 11 by the US Army on a federal website with the intent to canvas private organisations to establish whether they were capable of supplying the services.

Once this is established, the scale and fee would then be set.

The success of the Awakening campaign involved training and fighting militant tribesmen to take on al Qaeda.

Many of their leaders have indicated they would be prepared to do the same again - but would turn against IS only once Prime Minister Nouri al Maliki, a Shia, steps down.

He has now indicated he is prepared to stand aside in favour of Haider al Abadi, a fellow Shia with a reputation for reaching out across the sectarian divide.

Private contractors would, inevitably, be drawn from the ranks of retired special operations troops and spies who were so integral to the Awakening campaign.